Thursday 30 May 2013 03.00 EDT
First published on Thursday 30 May 2013 03.00 EDT

Last autumn David Cameron went to London's Imperial War Museum and announced plans for "a truly national commemoration" of the centenary of the first world war. There would be, he revealed, four years of events and activity, all at a total cost of more than £50m, starting with the centenary of the outbreak of war in August 2014 and continuing until the centenary of the Armistice in November 2018.

The speech was strikingly personal. Cameron talked about his own family experience of war. He said how Robert Graves's war memoir, Goodbye to All That, was "my favourite book". And he spoke of the great impression – "one of the most powerful things I've ever seen" – made on him by a visit to the Turkish memorial at Gallipoli. That memorial's inscription – which states "there is no difference between the Johnnies and the Mehmets to us, where they lie, side by side, in this country of ours" – managed to capture "so much of what this is all about", the prime minister said.

What, though, is this promised 1914-18 commemoration all about? We don't yet know. This is a government with a prejudice in favour of history – good – but some deep prejudices about history – bad. In his speech, Cameron said that the purpose was "to honour those who served; to remember those who died; and to ensure that the lessons learned live with us for ever". That's OK as far as it goes. But, crucially, he did not attempt the hard bit – spelling out what those lessons are.

This is not surprising because, to put it mildly, the lessons of the first world war are not a settled question in modern Britain, even after nearly 100 years. That the war should be commemorated ought not to be an issue. It is a living part of the shared past. But how it should be marked cannot help but be a source of argument. A traditional sequence of parades and services attended by monarchs, politicians and generals fails to come close to what is required.

Nearly a million British soldiers died between 1914 and 1918. There had never been a collective national and community trauma like it. Most soldiers probably set out thinking they were fighting for king and country against an aggressive German foe. But not all of them did. Meanwhile many of those who returned did so with more complex, more conflicted and much darker feelings and experiences. Unless all these things are properly reflected at the official level, the official commemoration is not just pointless, it is a deliberate deception, a lie.

This official commemoration will be happening in a country whose shared national narrative is fraying before our eyes. The most important lesson of the European wars of the 20th century is that most of Europe has now opted for peace and co-operation instead of war. But is a Britain that bridles at European co-operation and struggles to be at ease with anything except the old imperial identity a country that embraces that lesson? Can a Britain divided by today's wars be a Britain at ease with those of yesteryear?

Eight months on from the Cameron speech, a fuller programme for the first world war commemorations has not yet been announced. The few hints that have emerged are contradictory. A planned re-enactment of the 1914 Christmas truce football game on the western front might be harmless enough as long as it isn't oversold as a truly representative event of a conflict that was characterised by carnage not games. A rumoured Anglo-German religious service at a military cemetery near Mons is more promising, though a bit minimal. Shamefully, Cameron's original speech made no reference of any kind to shared events with Germany, or of the importance of reconciliation, so perhaps there has been some rethinking. There is talk of a further statement by the culture secretary, Maria Miller, in June.

Characteristically, Alex Salmond hit a more confident note when he announced Scotland's separate plans last week. The commemorations were "in no sense a celebration of this devastating conflict", he said. Commemorative plans in Ireland are even more nuanced. But Conservatives cannot bring themselves to use subtle or new language to describe the first world war and they are therefore blighting the possibility of a credible, modern, UK-wide commemoration.

Take the disturbing case of Andrew Murrison MP, a former naval doctor and now a junior minister at the ministry of defence. In 2012 Cameron appointed Murrison as his "special representative" on the committee charged with drawing up the anniversary programme. But if Murrison's recent views represent those of the prime minister, it should set alarm bells ringing, especially among those who bridle at the continuing insouciant use, by Cameron, Murrison and others, of the term great war.

In March this year, Murrison gave a speech to a conference on schools and the centenary held at Wellington public school. The most striking line in his speech was his endorsement of the 1914-18 conflict as "a just war". After sneering at those who, "equipped with your wonderful retrospectoscope" see the war as "a cataclysmic political failure", Murrison added that "to dismiss the centenary of the war to end all wars would in my view breach the military covenant". The commemorations, said Murrison, "would bring us together as a nation, and especially the Commonwealth".

This was the speech of a man who is out of his depth. Or, to put it another way, it was the speech of someone who cannot think about British history outside the box of the imperial military past. This is a past in which, essentially, war and the soldiery unite the nation under its rulers and their aims. But we do not really inhabit such a Britain today, in spite of energetic pretences to the contrary. Many, probably a majority, think our soldiers are heroes. Some think the language of heroism has become too cheap and indiscriminate. A few fanatics believe our soldiers are committing crimes against Islam. Others, as Wednesday's news from Afghanistan underscores, fear they are too often guilty of human rights abuses.

In the Britain of 2013 it is absurd to pretend that our armed forces fight just wars in which they invariably behave heroically against evil enemies in actions for which they deserve undivided honour. It is not like that today. And it was not like that in the first world war either, with far more catastrophic consequences. It is pathetic to pretend otherwise. But those who deceive themselves about the present also deceive themselves about the past.

• Comments on this thread will be switched on at 9am on Thursday 30 May